In recent years, the field sequential system as one of driving systems of a liquid crystal, display device, which displays a color image, has been developed. In the field sequential system, by sequentially switching light emitting elements such as cathode fluorescent lamps (CCFL) and light emitting diodes (LED) of red (R) light, green (G) light, and blue (B) light as light of a backlight and by sequentially supplying color data corresponding to colors of light of the respective light emitting elements to a liquid crystal panel in synchronization with the switching, transmission states thereof are controlled, whereby additive color mixing is performed on the retinas of an observer. According to the field sequential system, colors can be displayed even when a plurality of sub-pixels are not formed on a single pixel. Therefore, it is possible to achieve high resolution. Further, since the light from each light emitting element is directly used, it is not necessary to form a color filter in each pixel (color-filterless), and usage efficiencies of light of the respective light emitting elements are improved.
When an image is displayed on the liquid crystal panel through the field sequential system, for each sub-frame period, the light emitting elements provided in a backlight unit are sequentially switched, and a scanning operation is performed from the upper end to the lower end (or from the lower end to the upper end) of the screen.
For example, a description will be given of a case of displaying a red image on the liquid crystal panel through field sequential driving disclosed in PTL 1. FIG. 29 is a diagram illustrating display states of an image in respective sub-frame periods when an image is displayed on the liquid crystal panel through a field sequential system in the related art. More specifically, FIG. 29(a) is a diagram illustrating timing of supplying data for red image display to each pixel of the liquid crystal panel, and FIG. 29(b) is a diagram illustrating lighting start times and lighting time periods of light emitting elements of respective colors.
As illustrated in FIG. 29(a), a red light emitting element is turned on from a start time to an end time in a first sub-frame period. Further, the scanning operation from the upper end to the lower end of a screen is started at the start time, and transmission data (an opening portion indicated in FIG. 29(a)), which is for maximizing an amount of transmitted red light, is supplied as red data to each pixel. Thereby, the red light is transmitted through an area to which the red transmission data is supplied.
The red light emitting element is turned on from the start time to the end time in a second sub-frame period. Further, the scanning operation from the upper end to the lower end of a screen is started at the start time, and light blocking data (a hatched portion indicated in FIG. 29(a)), which is for minimizing the amount of transmitted red light, is supplied as red data to each pixel. Thereby, the red light is transmitted through an area in which the red transmission data remains.
The green light emitting element is turned on from the start time to the end time in a third sub-frame period. Further, the scanning operation from the upper end to the lower end of a screen is started at the start time, and light blocking data, which is for minimizing the amount of transmitted green light, is supplied as green data to each pixel. Thereby, light blocking data is supplied to all the pixels, and thus the green light cannot be transmitted through the liquid crystal panel.
Likewise, also in a fourth sub-frame period, the green light cannot be transmitted through the liquid crystal panel. Further, also in a fifth sub-frame period and a sixth sub-frame period, the blue light cannot be transmitted through the liquid crystal panel. Thereby, as illustrated in FIG. 29(b), a red image with no color unevenness is displayed on the liquid crystal panel.
Further, there is a presentation box described in NPL 1 as an application example of the image display device that displays an image on the liquid crystal panel through the above-mentioned field sequential system. On the front surface of the presentation box, a color-filterless liquid crystal panel is provided. An illumination unit, which illuminates the inside of the presentation box, employs red, green, and blue LEDs or CCFLs. In a similar manner to the liquid crystal display device disclosed in PTL 1, by appropriately controlling the light emitting timing of the illumination unit and the timing of controlling the transmission state of the liquid crystal panel, red light, green light, and blue light emitted from the illumination unit are respectively transmitted through the liquid crystal panel in accordance with the transmission states of the liquid crystal panel. Thereby, an observer, who is observing the presentation box, is able to view not only a color image, which is displayed on the liquid crystal panel provided on the front surface of the presentation box, but also an exhibited object which is exhibited inside the presentation box.